Davis started his coaching career as a quarterbacks/receivers coach at Barbe High School in Lake Charles, Louisiana. He served two seasons there, and then went on to become the quarterbacks coach for two seasons at Port Neches-Groves High School, his high school alma mater. He began his college coaching career as the quarterbacks coach under Tom Wilson and Jackie Sherrill at Texas A&M University. He was a part-time assistant at A&M in 1978, and then was named a full-time coach in 1979. He worked alongside Slocum, who then served as the defensive coordinator.

However, on December 6, 2010, after the worst season in the Mack Brown era at the University of Texas, Greg Davis resigned as offensive coordinator of the Longhorns. The 2010 season was the first season in 13 years the Longhorns failed to make a bowl game, and the first in nine seasons the Longhorns failed to reach 10 wins on the season.

After a year out of football, Davis was hired by Iowa for the 2012 season.